1. Field of Invention
This invention relates to a space launch method whereby a large transport aircraft with the assistance of other apparatus and aircraft tows an intended space load close to the stratosphere and performs specific maneuvers to transfer kinetic energy and a plurality of fuels from a plurality of tow vehicles and structures to the towed load, which will thereafter accelerate by an order of magnitude or more due to the effects of the transfers.
2. Prior Art
Inventors have proposed many methods by which a space vehicle would be propelled out of the Earth's atmosphere. All of the concepts on record in the patent database regarding means of space launch are at least theoretically possible. “Many are called, but few are chosen” is a general adage that particularly applies to the challenge of reaching earth orbit or beyond in a safe, reliable, economical, and operationally flexible fashion. The thrust of the arguments herein will focus on the shoals of practicality, where many previous theoretically acceptable concepts have foundered.
Giuliani, et all. in U.S. Pat. No. 4,709,883 (1987) uses a ground-based magnetic levitation and propulsion system (MAGLEV) to accelerate a launch vehicle in a circular pathway, or a launch vehicle plus a jet-engine tow vehicle. The jet tow vehicle would thereafter do a lot of the work in getting the launch vehicle to an altitude where it would proceed on its way independently. Giuliani proposes another embodiment wherein the circular MAGLEV pathway would be constructed on the moon. This seems like a superior utilization of the concept, but both embodiments suffer from the fact that the optimal launch trajectory would be in one plane. Three degrees of freedom in the launch trajectory could only be achieved by building the circular launch pathway on the equator of the Earth or the moon and then launching at a precise second on the 24-hour rotation cycle of the Earth or the 30-day rotation cycle of the moon, which is highly intolerant of other potential launch delays. Even adjusting the angle of inclination of the launch would be difficult, as the whole horizontal plane of the circular pathway would have to be tilted to avoid having the system look like a bent coin.
Worse yet, it is widely known that all launch systems work best when launching in a due-east direction, so as to take advantage of the earth's spin rate adding directly to the velocity of the launch load. Closer-to-the-equator-is-better is also a prime correlation of this principle. A ground level circular MAGLEV track, or any such fixed track, really then is going to preferentially point at one optimal orbit and anything more than about five degrees from that will be hard to get to. As space gets more congested, such a system obstructs itself after awhile.
Another problem with the ground level MAGLEV track (one that applies to every scheme that accelerates space vehicles to high velocities while still in the thick of the atmosphere) is what to do about heat due to aerodynamic friction and about buffeting due to ordinary turbulence. Any potential space vehicle that is moving much above Mach 1.5 at ground level is going to become pretty warm from aerodynamic heating by the time it exits the atmosphere, plus endure some shaking up.
It is hard to see an advantage of a ground-based MAGLEV approach unless it would be powerful enough to fling unassisted a load at least up to a level where the atmosphere is so thin that scram jets or rockets reign. If considerable assist is needed from air-breathing engines or rockets to reach the stratosphere, the question will always arise about whether the whole job would best be left to such means and skip the MAGLEV complication. To do the complete job without non-magnetic assistance the circular launching ring will probably have to be quite large in order to avoid accelerations beyond what humans can endure.
Moreover, the intended launch vehicle when it exits the MAGLEV ring will still be in the thick of the atmosphere at a very high velocity from ground level up. Hitting a bird or a hail stone at Mach 0.7 is one thing, hitting the same object at Mach 7 is quite another. It is a lot safer situation if a launch system does not generate the extreme velocities until the load is high above much of the atmosphere. As we all saw in the space shuttle Columbia disaster, sometimes the problem is simply something being forced or shaken off one part of the launch load by atmospheric resistance and then it runs into a following part. Airplanes are generally built to be surprisingly flexible because aircraft have to deal with the atmosphere all the time. Spacecraft are often constrained to be extremely rigid, which is why the space shuttles “chatter” so violently during the high velocity climb-out of the atmosphere and why some parts or accretions will always be prone to come loose. Presumably, the Giuliani system would have the space vehicle being launched already at a major portion of its peak velocity and at ground level atmospheric pressure, so the turbulence will probably be much more extreme than the space shuttle (which accelerates vertically more gradually and only goes faster as the atmosphere is thinning) must endure.
Kelly, in U.S. Pat. No. 5,626,310 (1997) and U.S. Pat. No. 6,029,928 (2000) admirably, even exhaustively, describes the advantages of tow vehicles pulling intended space vehicles to altitudes of ten kilometers or greater for launch, thus reducing the need of a powerful first stage rocket booster or other means of boosting the space launch vehicle to high altitudes prior to ignition of the space vehicle's own propulsion system. Kelly also strongly emphasizes the virtues of a space launch vehicle being configured as a winged glider or aircraft so that it may aerodynamically support all of its own weight during takeoff, ascent, and air launch, which in this case would merely be separation from the tow cable at a subsonic speed. Scott, U.S. Pat. No. 6,193,187 (2001) offers a non-tow cargo bay system.
In all of his claims Kelly contemplates that the separation must take place at subsonic speeds. One would think that if being towed to a high altitude is such an advantage for a spacecraft, being towed to a high altitude and released at a speed greater than the speed of sound would be an even greater advantage.
In actuality, Kelly's space launch vehicle is only the first stage of a multi-stage rocket in disguise. It is an admirable first stage in that it does enable the conventional tow aircraft out in front to tug a lot heavier load up to 10 kilometers or so of altitude than the tow aircraft could possibly carry attached anywhere to its fuselage (by a factor of five, according to Kelly.) Kelly documents that advantage very well. Kelly's space vehicle is a laudable first stage in that, after it detaches from the tow and thereafter uses its own rocket motor and fuel to take the actual launch load much higher (about a factor of 8 or to 80 kms), it will coast for awhile above the sensible atmosphere before it opens up and allows the launch load to use its own motor to go on its way. Actually, a nose door opens up and big springs or some other mechanism must push the launch load out and away from the space launch glider, imparting just enough velocity that the launch load will create adequate distance to light its rocket motors without scorching the first stage space launch glider. Kelly's space launch glider would then then be light enough to endure the heat of re-entry without much problem, although it will require shuttle-type heat resistant tiling. Kelly claims that turn-around time on the ground will be quite short and, presumably, the turn-around time for the conventional tanker aircraft would also be short so that two launches a day would not be unfeasible.
It is hard to view either the 1997 Kelly concept or the 2000 follow-on as being suitable for manned flight. In his drawings Kelly puts the launch load basically inside the first stage rocket, between two large liquid fuel tanks (the conventional tow aircraft is considered as being the zero-stage rocket.) Some type of ejection seat pathway would have to be provided to propel the astronauts from inside two vessels in event of mishap during takeoff or the leisurely ascent climb. In actuality, Kelly's space launch glider rather severely limits the size of a launch load to what fits inside its payload bay, as does the Scott system.
None of Kelly's many claims to my knowledge has ever been attempted in an actual space launch, although modeling in wind tunnels, decompression chambers, or elaborate computer simulations may have been done. Neither Kelly nor any references cited by Kelly describe or claim an exchange of significant angular momentum between the tow vehicle and the tow line to the towed vehicle, nor mention any means by which the velocity of the towed vehicle could significantly exceed the velocity of the towing vehicle at the instant of separation and prior to ignition of the space vehicle motor.
Wittmann, et al, U.S. Pat. No. 4,303,214 (1981) Assignee: Hughes Aircraft, describes an apparatus for the gyroscopic ejection of a shuttle launched spacecraft. Particularly, Wittmann concentrates on the problem of launching geostationary satellites from the cargo bay of the U.S. space shuttle in use at that time. Wittmann proposed that the gyroscopic ejection would impart both linear and angular momentum to the satellite at separation from the shuttle, the energy coming partially from a compressed spring in the apparatus and partially from any spin of the space shuttle itself around its own center of gravity. The angular momentum due to spin imparted to the satellite is intended in Wittmann to provide gyroscopic stability to the satellite as it uses its own rocket power to climb to a much higher orbit than the space shuttle could achieve. No cable, tether, or tow line is used in Wittmann's invention for the imparting or transfer of any component of momentum. To Wittmann et all the use of a very slight amount of centripetal force was only a convenient way to get space loads clear of a payload bay, an approach frequently exhibited by inventors in this field such as Kelly, Scott, or Peterson, U.S. Pat. No. 4,646,994, (1987) p. 1.
Piasecki, in U.S. Pat. No. 5,188,313 (1993) describes a towing frame and a computer control system intended to optimize performance of a towing aircraft/towed vehicle pair. Piasecki utilizes a unique towing frame that would intermediate between the tow vehicle and vehicles being towed. Piasecki also discusses the possibility of fuel transfer between towed and towing vehicles, in either direction, but primarily from the towed vehicle forward to the towing vehicle, to increase its range.
It is no disrespect to the inventor to assume that the transparent object of the Piasecki research was to win a defense contract to extend the range and endurance of helicopters. Either conventional helicopters or conventional fixed wing aircraft can greatly extend their range by towing a glider loaded with fuel. The glider would download fuel as needed to the drinking vehicle through a hose associated with the tow line. As Kelly argued in his patent, however, it is better if the vehicle being towed be not only behind, but above the towing vehicle, so as to avoid turbulence created by the towing aircraft. This obviously creates a problem for helicopters. Unless the pilot is paying constant attention, the tow line/hose will get into the helicopter's rotors.
The 1993 Piasecki patent regarding the towing frame appears to have been an attempt to put a device behind the helicopter that could keep the tow/fuel lines clear without needing much monitoring by the pilot. The Piasecki device would probably work, but the defense department apparently decided that the more functional solution would be the Boeing tilt rotor wing Osprey or simply building more efficient, longer-range helicopters. The Piasecki towing frame and fuel-carrying glider would at any rate have been a nightmare paired with a helicopter on the crowded deck of an aircraft carrier.
Nothing in Piasecki refers to winged glider spacecraft or any space vehicle being towed for airborne launch. To my knowledge, no practical, real use of the system Piasecki describes has ever come about, not even in the odd attempt at endurance flying for the record books.
Hardy, et al, U.S. Pat. No. 4,802,639 (1989) Assignee: Boeing, extensively discusses ferry-type space launches in which the intended space vehicle is carried to high altitude by a jet, scram-jet, or rocket-powered aircraft, then released to proceed on its own rocket power. Hardy talks about struts on which the space orbiter will pivot down and away from the aircraft, but no increase in the velocity of the orbiter vehicle due to the pivoting motion itself is mentioned. Hardy envisions separation of the aircraft/orbiter pair at a Mach number of about 3.3. In a second embodiment, the main engine of the orbiter would be a scramjet.
One problem that the Hardy system must overcome is the “bounce” that two objects impose on each other when they separate from such close contact at a high Mach number. It may not be possible to accurately model every possible contingency and variable in that extreme situation. Actual practice can be a hard and expensive way to learn.
Another important concept, found in Clapp, et al. U.S. Pat. No. 6,658,863 (2000) envisions a basically conventional refueling aircraft that internally transports liquid oxygen for transfer in flight to a space vehicle that takes off independently, obviating the need to spend energy transporting this heavy rocket fuel component to launch altitude. Clapp envisions discharging the liquid oxygen oxidizer from the aircraft in which it was transported to the rocket-propelled space orbiter via a conventional trailing-hose refueling arrangement with the use of pumps already developed for moving liquid oxygen and with the assistance of stainless steel bellows, stainless steel braided cable, and/or a gaseous pressurant such as helium
Clapp, et al. specifies that its rocketplane/potential space orbiter in the Clapp preferred embodiment would take off from ground level powered by two conventional GE military jet engines. It would then rendezvous with the tanker airplane to fuel up with liquid oxygen or another oxidizer, such as hydrogen peroxide. Clapp suggests a variety of aircraft that could be adopted to the tanker role, including the Boeing 707 or 747, the Lockheed L1011, the Douglas DC-10, existing KC-135 tanker aircraft, and the C-17.
The first major disadvantage of the Clapp scheme is that the Clapp rocketplane will require two separate major fuel systems because it is also a jet plane with two F-16 fighter engines. The rocketplane would fly as a conventional jet to the rendezvous altitude with the tanker, then it will have to mate with that tanker. The normal tendency during typical airborne refueling at the highest allowable altitude is for both aircraft to simultaneously slow and to lose altitude during the procedure unless the “drinking” aircraft increases power significantly, for the reason that the fuel-receiving aircraft is getting heavier and slower as it takes on fuel. The tanker is getting lighter and faster, naturally wanting to ascend unless it backs off on throttle. Therefore either both aircraft are going to tend to slow down and descend a little bit, or both are going to tend to ascend. Maintaining stasis takes effort.
Whatever the drinking aircraft does, it can't avoid wasting a percentage of its total fuel use for the flight, as it either has to surrender speed and altitude it just paid to achieve, or it has to carry extra jet fuel along so that it can keep up with the tanker aircraft as the latter's load lightens and performance improves. What the Clapp rocketplane also probably can't do in this situation is fire up its rocket engine and burn liquid oxygen even as it takes that substance on from the mother ship ahead of it. Even in the unlikely situation that safety concerns are waived and ignition is allowed for a throttleable rocket, the Clapp rocketplane still would have to waste liquid oxygen and other rocket fuel as it loafs along at an inefficient pace for a rocket motor while the delicate fueling process proceeds. Due to the very high purity requirement for most oxidizers, absolutely no fuel tanks, lines, or valves used for jet fuel can be utilized for the volatile, cryogenic oxidizers. Jet fuel can replace kerosene in some rocket engines, however, a plus for the Clapp scheme.
For the Clapp design and all the other prior art ideas intent on exploiting the alluring, positive aspects of tow space launches, there seems to be only lose-lose or at best win-lose outcomes available. But now it is time to show the path to win-win.